This video shows the weekend outlook.
During the day tomorrow, it appears a band of heavy rain will affect areas near the coast or just offshore from New Jersey to Massachusetts. That moisture may move away for the afternoon, but thunderstorms will erupt farther west where morning and midday sunshine adds fuel to growing cumulus clouds. This forecast map from the main U.S. model suggests little or no rain in the I-95 corridor from Maryland to Maine tomorrow afternoon.
Cooling aloft and heating moist air closer to the ground should trigger strong thunderstorms from eastern New York and much of New England southwest through parts of the Middle Atlantic states.
The front will move into a region with high humidity as it approaches the I95 corridor tomorrow. This is the basis for SPC's forecast of thunderstorms approaching severe limits tomorrow.
Tropical Storm Colin is caught in the southern stream while the northern stream is helping to send unseasonably cool air out of central Canada.
Then, as the cold front arrives, there may be violent thunderstorms. This map shows the early morning SPC assessment of the severe weather risk on Sunday:
Farther east on Sunday, rain is likely to be more extensive, and there is a severe thunderstorm threat from the Middle Atlantic region on south.
With the second front, shower activity may be spotty at first as the system comes through Chicago on Saturday but could be wetter and more stormy than the first front by time it reaches the I-95 corridor Sunday.